Circuit interrupters



June 26, 1956 w. M. LEEDS 2,752,460

CIRCUIT INTERRUPTERS Filed April 10, 1953 6 Sheets-Sheet 1 Fig. I.

Insulation 5 Insulation Insulation WITNESSES! INVENTOR W/QW 63 6 BY K ATTOR Y Winthrop M.Leeds.

June 26, 1956 w. M. LEEDS 2,752,450

cmcuu INTERRUPTERS Filed April 10, 1953 6 Sheets-Sheet 2 Fig.2.

WITNESSES: INVENTOR 4717 a BY lg ATTORNE Winthrop M. Leeds.

June 26, 1956 w. M. LEEDS 2,752,460

cmcun INTERRUPTERS Filed April 10, 1955 e Sheets-Sheet s WITNESSES: INVENTOR Winthrop M. Leeds.

June 26, 1956 w. M. LEEDS 2,752,460

CIRCUIT INTERRUPTEIRS Filed April 10, 1953 6 Sheets-Sheet 4 Fig.6.

INVENTOR Winthrop M. Leeds.

BY 71] x ATTORNEY June 26, 1956 w. M. LEEDS 2,752,460

CIRCUIT INTERRUPTERS Filed April 10, 1953 s Sheets-Sheet s WITNESSES: INVENTOR f- Winthrop M.Leeds.

June 26, 1956 w. M. LEEDS 2,752,460

CIRCUIT INTERRUPTERS Filed April 10, 1953 6 Sheets-Sheet 6 Flg. p

WITNESSES: INVENTOR 5.427%? Winthrop M.Leeds.

ATTORNE United States Patent CIRCUIT INTERRUPTERS Winthrop M. Leeds, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 10, 1953, Serial No. 348,068

11 Claims. (Cl. 200*150) This invention relates to circuit interrupters in general, and, more particularly, to arc-extinguishing structures therefor.

It is a general object of my invention to provide an improved and highly effective circuit interrupter for interrupting a wide range of current values.

In the recent rapid progress of circuit interrupters, they have been .applied commercially over a wide range of voltages and currents. The power requirements have steadily increased up to the point where at the present time it is desirable to produce circuit interrupters having suificient interrupting capacity to interrupt power ranging upwardly to 25 million kva. The voltages at these powers may vary all the way from 138 kv. to 330 kv. The currents to be interrupted may range from 25,000 to 50,000 amperes and over. Certain difiiculties arise during the interruption of these very high powers, and it is an object of my invention to increase the rating of certain interrupting units, say of the type set out in U. S. Patent 2,467,760, for the interruption of such powers.

It has been found that in the interruption of such extremely high powers, and for the interruption of high current values, that the orifices of circuit interrupters of the type set out in the aforesaid patent appear to clog, say for currents above about 20,000 amperes, and back pressure created at the interrupting are not only tends to force the grid plates apart, but allows backflow from the interrupting arc. Larger orifices to improve high-current operation makes low-current performance unsatisfactory. The present invention solves the foregoing difliculty.

Generally, the invention comprises sending normal oil flow, or fiuid flow, to the interrupting arc and permitting normal venting to take place from the interrupting arc. The usual interrupting action is thereby obtained when interrupting low and medium fault currents. For very high currents, above say 20,000 amperes, an overpressure valve opens to permit auxiliary exhausting from the interrupting are. Not only does the actuation of the overpressure valve relieve the excessive pressure within the interrupting unit, but also desirable additional interrupting action is brought to bear upon the interrupting are, as more fully explained hereinafter.

It is a further object of my invention to provide an improved circuit interrupter operable over a wide current range by having valr e means controlling an auxiliary venting means and operable only during high current interruption.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

Figure 1 is a side elevational view, partially in section, of a circuit interrupter embodying my invention, and the contact structure being shown in the closed-circuit position;

Fig. 2 is an enlarged, vertical sectional view through the left-hand arc-extinguishing unit of Fig. 1, the contact ice structure being shown in the partially open-circuit position;

Fig. 3 is a sectional view taken along the line III-III of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a sectional view, similar to that shown in Fig. 3, but depicting a slightly modified type of extinguishing unit in which unrestricted venting'may take place at the lower end of the unit upon functioning of the overpressure valve;

Fig. 5 is a sectional view taken along the line VV of Fig. 6 looking in the direction of the arrows;

Fig. 6 is a vertical sectional view through a modified type of interrupting unit, the contact structure being shown in the partially open-circuit position;

Fig. 7 is an enlarged perspective view of the slide valve utilized in the embodiment of the invention shown in Fig. 6;

Fig. 8 is a vertical sectional view through a modified type of extinguishing unit, identical to that of Figs. 5 and 6, but utilizing a slightly diiferent slide valve to obtain restricted venting near the lower end of the unit upon functioning of the overpressure valve;

Fig. 9 is a sectional view taken through a modified type of extinguishing unit, similar to the type set out in Figs. 5 and 6, but providing a contact slide-valve action to take place near the lower end of the extinguishing unit during high-current interruption; and,

Fig. 10 is a vertical sectional view through still another modified type of extinguishing unit employing a different type of overpressure valve.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral 1 designates a tank filled to the level 2 with a suitable arc-extinguishing fluid 3, in this instance circuit breaker oil. Extending through the cover 5 of the tank 1 are a pair of terminal bushings 6, 7, from the lower ends of which depend arcextinguishing units, generally designated by the reference numeral 9.

Electrically interconnecting the two arc-extinguishing units 9 in series is a movable conducting bridging member 10, vertically actuated in a reciprocal manner by an insulating operating rod 11. The lift rod 11 may be actuated by any suitable operating mechanism, which forms no part of my invention.

The opposite outer ends of the bridging member 10 are upturned, as shown in Fig. 2, to form lower movable rod-shaped interrupting contacts 12. Each interrupting contact 12 makes abutting engagement with a relatively stationary intermediate contact, designated by the reference numeral 14 and biased downwardly by a compression spring 15. It will be noted that the intermediate contact 14 has only slight vertical axial movement. It remains in a substantially stationary position.

The coil spring 15 has its lower seat upon a fiange 16 integrally formed with the intermediate contact 14. The upper end of the compression spring 15 bears against an apertured plate 17, as more clearly shown in Fig. 2 of the drawings.

Making abutting engagement with the upper end of the intermediate contact 14 is a movable, rotatable, pressuregenerating contact 19, pivotally mounted, as at 20, and actuated externally of the arc-extinguishing unit 9 by a side insulating operating rod 21. The operating rod 21 has a lower cap 22, which is picked up by the bridging member 10 near the end of the closing operation, and which forms a lower seat for a compression spring 23. The upper end of the compression spring 23 rests against the lower insulating plate 24 of the unit 9, as shown in Fig. 2.

Due to the biasing action exerted by the compression spring 23, the side operating rod 21 tends to remain in engagement with the bridging contact 10 during the opening operation. A pin 25 passes through the upper end of the operating rod 21, and also passes through two enlarged apertures 26 provided in two externally extending legs 2'7, jutting outwardly from the shaft 29 of the pressure-generating contact 19. Thus, the pressure-generating contact 19 is actuated by rotative motion of the legs 27, as effected by the side operating rod 21.

A flange 23 is fixedly secured to the side operating rod 211, and serves as a lower seat for a contact compression spring 29, the upper end of which bears against a washer 3t) slidably mounted on the rod 21 and bearing against lower sides of the two legs 27, as shown in Fig. 2.

During the closing operation the lower movable rodshaped interrupting contact 12 strikes the intermediate contact 14 prior to engagement thereof with the pressuregenerating contact 19, so that the intermediate contact 14 is slightly moved upwardly, raising the flange 16 upwardly away from the plate 31. At this time the pressure-generating contact 19 strikes the upper end of the intermediate contact 14. Continued upward closing travel of the bridging contact it) causesslightly additional vertical travel of the intermediate contact 14, further compressing the spring 35, and moving the pin 25 of the side operating rod 21 upwardly within the enlarged apertures 26, so that the contact compression spring 29 provides the requisite contact pressure between the three contacts 12, 14 and 19.

During the opening operation the bridging contact moves downwardly, establishing an interrupting arc 32 progressively along an arcing passage 33. The compression spring 23 causes lowering of the operating rod 21 with the bridging member 10, thereby causing the pin 25 to engage the lower sides of the apertures 26 forcibly causing clockwise rotative travel of the legs 27, and upward separating movement of the pressure-generating contact 19 away from the intermediate contact 14 to establish a pressure-generating are 35 within a pressure-generating chamber 36, as shown in Fig. 2.

Suitable insulating and configured plate structure is provided, as shown in Fig. 2, forming a first passage 38 interconnecting the pressure-generating chamber 36 and pressure-generating arc 35 with a plurality of inlet passages 39. The configuration or" the inlet passages 39 is more clearly shown in Fig. 3 of the drawings. Disposed immediately adjacent to the inlet passages 39 are orifice plates, designated by the reference numeral 40, and providing a series of spaced orifices 41, through which the rod-shaped movable interrupting contact 12 passes.

Disposed on the other sides of the orifice plates 40 from the inlet passages 39 are first, normally open venting means, generally designated by the reference character 42, and comprising a plurality of spaced pairs of plates 43. Each pair of plates 43 comprises two laterally spaced halfplate portions 44, the configuration of which is more readily apparent from an inspection of Fig. 3 of the drawings. A plurality of insulating tie-rods 45 and nuts 46 maintain the several insulating plates in contiguous relationship.

On the opposite side of the interrupting contact 12 from the inlet passages 39 are a plurality of spaced exhaust passages 48. As shown in Fig. 3, each exhaust passage 48 is provided with a restriction 49 disposed immediately adjacent to the interrupting contact 12, so that during the opening operation the interrupting contact 12 functions as a slide valve in successively uncovering the exhaust pas- ;ages 48. This action is apparent from an inspection of ig. 3. I

I provide a second venting means 5!), which is connected with the exhaust passages 48 by a second fluid transmitting passage, generally designated by the reference numeral 51. As noted in Fig. 2, the first and second passages 38 and 51, respectively, are formed upon the alignment of suitable apertures 52, 53 provided in the several insulating plates.

Overpressure valve means 54 is associated with the second venting means 50, and inthis particularinstan'ce comprises a valve 55 biased to the'closed position by a valve spring 56, the latter having a lower seat against an apertured plate 57, secured by screws 58 to the lower insulating plate 24 of the arc-extinguishing unit 9. An inlet valve 59 is preferably associated with the pressure-generating chamber 36 to close during the opening operation, and to open following the conclusion of the opening operation so as to permit fresh fluid to enter the unit 9 through apertures 60 provided in the top dome casting 61 of the unit 9.

The operation of the embodiment of my invention shown in Figs. l3 will now be explained. Assuming the interruption of low and medium fault currents, the overpressure valve means 54 will not open. In other words, the valve 55 will remain closed, and fluid, in this instance oil, will only be permittedto pass out of the unit 9 through the normally open venting means 42; and there will result the usual multi-flow interrupting action, as provided by the multi-orifice interrupting structure 62 disposed adjacent to the interrupting are 32. As brought out in the aforesaid patent, liquid will flow downwardly through the first passage 33 and through the several inlet passages 39, through the orifices 41, and into engagement with the interrupting are 32. The liquid will then exhaust out of the unit 9 through the opposed pairs of venting passages 63, as provided by the spaces between the laterally spaced half plates 44. Interruption will soon follow, and the bridging memberlt) will continue downwardly to the disconnecting position, indicated by the chain lines 64 in Fig. 1.

During the interruption of very high currents, say above 20,000 amperes, the overpressure valve means 54 will function so that the valve 55 will move downwardly away from its seat, against the spring pressure exerted by the valve spring 56, to permit auxiliary exhausting of liquid downwardly through the second fluid transmitting passage 51. Not only will this provide a release of pressure within the unit 9, but also there will occur additional interrupting action brought to bear upon the interrupting are 32, as provided by the cross-blast action. In other words, not only will liquid flow from the inlet passages 39 through the orifices 41 and out through the venting passages 63, but also liquid will flow directly across the arc passage 33, as afforded by the disposition of the inlet and exhaust passages 39, 48 on the same level (Fig. 2).

Consequently, upon opening of the overpressure valve means 54, or opening of the second venting means 50 cross-blast action will be combined with the usual multiorifice action for effective interruption of the interrupting are 32.

During the interruption of high fault currents, as occurred during the opening of the second venting means 50 by operation of the overpressure valve means '54, the restrictions 49 in the exhaust passages 48 prevented any substantial leakage of liquid below the tip 65 of the interrupting contact 12. 111 other words, during the opening operation the interrupting contact 12 functioned additionally as a slide valve in successively uncovering the exhaust passages 48 so that most effective utilization of the liquid flow out through the second venting means 50 was obtained. There occurred substantially no leakage out through the exhaust passages 43'below the tip 65 of the interrupting contact 12. This may be desirable when the interrupter is applied to extremely high-voltage circuits, where the magnitude of fault currents is not too high.

However, for the case where the interrupter is applied on relatively low-voltage circuits, say for example, to circuits of 138 kv. or 161 kv., for extremely high powers, where very high magnitude fault currents are encountered, it may be desirable to permit venting to take place below' the tip 65 of the interrupting contact 12 when the overpressure valve means 54 opens. In such circumstances, the presence of the restrictions 49 may not be desirable.

Fig. 4 shows a slightly modified type of interrupting uni-t, generally designated by the reference character 67, which is identical to the unit 9 of Fig. 2 with the exception that the restrictions 49 in the exhaust passages 48 are omitted. Thus leakage will occur below the tip 65 of the interrupting contact 12 upon opening of the overpressure valve means 54. This will result in a leakage of fluid below the tip 65, with no interrupting action obtained by this leakage; but on the other hand, for such very high currents to be interrupted, such additional leakage below the tip 65 of the movable contact 12 provides a desired relief of pressure from the interior of the arc-extinguishing unit 67.

In the embodiment of my invention shown in Figs. 5-7 the contact structure is identical to that heretofore described, and consequently a description thereof will not be repeated. In the modified type of interrupting unit, generally designated by the reference numeral 68,

- the first passage means 38 is disposed on the other side of the unit 68, so that venting will occur on the side of the unit 68 away from the other serially related unit 68. This will prevent a comingling of the exhaust gases and a possible voltage breakdown between the units 68.

Instead of using an exhaust valve of the type designated by the reference numeral 55 in Fig. 2, a slide valve 55a is employed, which is shown in perspective in Fig. 7. The slide valve 55a has a plurality of annular recesses 69, which line up with the exhaust passages 70 upon functioning of the slide valve 55a. A valve spring 56a biases the slide valve 55a toward its closed position, as shown in Fig. 6. The spring 56a is disposed within a vented cup 71, secured to the lower plate 24a of the unit 68. Pressure from the pressure-generating are 35, acting within the pressure-generating chamber 36, acts upon the top surface 74 of the slide valve 5511. This pressure also acts through a passage 75 to the region 76 and upwardly on the annular area 77. The net force, therefore, which serves to move the slide valve 55a downwardly is the pressure P within the pressuregenerating chamber 36 acting across the cross-sectional area of the rod portion 78 moving out through the aperture 79 in the lower insulating plate 24a. The valve spring 56a, therefore, is selected to act against the pressure P times the cross-sectional area of the rod portion 78.

During the interruption of low and medium fault currents the slide valve 55:! remains closed, and the usual multi-orifice action takes place, the fluid exhausting out of the opposed exhaust passages 63 of the first, normally open venting means 42.

During the interruption of high fault currents, the increased pressure P within the pressure-generating chamber 36 will act downwardly on the slide valve 55a with a force equal to the pressure P times the effective area A of the rod portion 78 passing through the plate 24a to cause slight compression of the valve spring 56a. This will serve to simultaneously open the spaced exhaust passages 70, thereby permitting cross-blast action to take place. It will be noted from an inspection of Fig. 5 that leakage will take place below the tip 65 of the interrupting contact 12 in the same manner as described above in connection with the embodiment of Fig. 4.

For the application of the interrupter 68 to the case of extremely high voltages, where the magnitude of the fault current may not be so high, and it is desirable to prevent leakage below the tip 65 of the interrupting contact 12, the inlet and exhaust passages may be narrowed to form a restriction 89 adjacent the interruption contact 12, as shown in Pig. 9 of the drawings. Fig. 9, therefore, shows a modified unit 81 in which the interrupting contact 12 functions as a slide valve because of the presence of the restrictions 80 in the inlet and exhaust passages 39, 70.

Another manner of preventing leakage adjacent the lower end of the unit is shown in Fig. 8 of the drawings,

which represents a modified unit 82, in all respects identical to the unit 68 of Fig. 6, but having a slightly different slide valve 55b. The slide valve 55b omits the recesses 69 adjacent the lower end thereof, so that venting through the second venting means 50 is only possible through the top exhaust passages 70. Consequently, Fig. 8 shows an interrupter suitable for use on very high-voltage circuits, where the magnitude of the fault current is not extremely high.

Fig. 10 shows a modified type of interrupting unit, generally designated by the reference numeral 84, having a valve 85 of the poppet type. The valve 85 has an upper portion 86, which is subjected to the pressure P within the pressure-generating chamber 36. The region 87 below the piston member 86 is vented to the region externally of the unit 84 by a vent passage 88. The valve 85 has a valve rod portion 89 to which are loosely secured a plurality of valves 90. Each valve 98 seats against an opening 91 which leads to the region externally of the unit 84 by venting passages 92 or 88, as shown in Fig. 10.

Fig. 10 hence shows a modified type of unit 84, which functions along the lines of those heretofore described and merely involves a modified type of valve 85 for the second venting means St The arrangement of Fig. 10 could either be used where venting occurs below the tip 65 of the movable contact 12, as was the case in Fig. 5, or restrictions could be provided in the plate structure, as indicated in Fig. 9, to provide a slide-valve function of the movable contact 12, as described above in connection with Figs. 3 and 9 of the drawings.

From the foregoing it will be apparent that l have provided a novel type of circuit interrupter suitable for use over a wide current and voltage range. During normal operation, that is when interrupting relatively low and medium fault currents, the overpressure valve means 54 does not function, and normal interrupting action takes place with the fluid exhausted through the first, normally open venting means 42. During the interruption of very high currents the overpressure valve means 54 functions to not only relieve the excessive pressure, but also to provide desirable cross-blast action for additional interruption influence brought to bear upon the interrupting are 32.

Although throughout the specification I have specified particular values of powers, voltages and currents, it is to be clearly understood that the sa. e w re merely for illustrative purposes, and were not intended to be limitations upon my invention. Those skilled in the art will know that my invention is applicable to high or low voltage circuits or dilferent current ranges, and that by a suitable proportioning of the parts and by a proper selection of spring pressures the device may be widely applied. The foregoing numerical examples were merely given to show certain possible commercial applications, but this by no means prohibits the use of the invention on other voltages or currents.

Although I have shown and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

I claim as my invention:

1. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating are within the unit, an interrupting arc passage within the unit, contact means including a movable contact for establishing an interrupting are along the interrupting arc passage, a first venting means associated with the interrupting arc passage permitting exhaust of fluid from the unit, said first venting means adapted to be opened while the said movable contact is in the interrupting arc passage, a first fluid-transmitting passage interconnecting the pressure-generating arc with the interrupting arc passage, a second valve-controlled venting means permitting exhaust of fluid from the unit, a secondfluid-transmitting passage leading from the interrupting arc passage to said second valve-controlled venting means, valve means responsive to the magnitude of the current being interrupted within the arc-extinguishing unit to open the second venting means, and opening of the second venting means causing fluid to flow against the interrupting are for additional interrupting action.

2. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating arc and an interrupting are within the unit, an interrupting structure disposed adjacent the interrupting arc and having a first normally-open venting means associated therewith to exhaust fluid from the unit, said first normally-open venting means being open, at all a first fluid-transmitting passage interconn pressure-generating arc with the interrupting structu a second normally-closed venting means to exhaust fluid from the unit, a second fluid-transmitting passage leading from the intcrrupti structure to said second venting means, valve means responsive to the magnitude of the current beim interrupted to open the second venting means, and openi of the second venting means causing fluid to flow the interrupting are for additional interrupting action.

3. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating are within the unit, contact means including a movable contact "for establishing an interrupting are within the unit, a multi-orifice interrupting structure disposed adjacent the interrupting arc and having a first venting means associated therewith, said first venting means permitting exhaust of fluid from the unit and being operable while the movable contact is in the unit, a first fluidtransmitting passage interconnecting the pressure-generating arc with the multi-orifiee interrupting structure, a second venting means permitting exhaust of fluid from the unit, a second fluid-transmitting passage leading from the multi-orifice interrupting structure to said second venting means, valve means responsive to the magnitude of the current being interrupted to open the second venting means, and actuation of the second venting means causing fluid to flow against the interrupting are for additional extinguishing action.

4. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating arc and an interrupting are within the unit, a multi-orifice interrupting structure disposed adjacent the interrupting are and having a first normallyopen venting means associated therewith, said first normally-open venting means permitting the exhaust of fluid from the unit and being operative during the entire period of establishing the interrupting are, a first fluid-transmitting passage interconnecting the pressure-generating arc with the multi-orifice interrupting structure, a second normally-closed venting means independent from the first venting means for exhausting fluid from the unit at a different location from the first venting means, a second fluid-transmitting passage leading from the multi-orifice interrupting structure to said second venting means, valve means responsive to the magnitude of the current being interrupted to open the second venting means and opening of the second venting means causing fluid to flow against the interrupting are for further extinguishing action.

5. A circuit interrupter including an arc-extinguishing unit immersed in an arc-extinguishingliquid, a pressuregenerating contact separable from an intermediate contact to establish a pressure-generating are, an arcing passage, a rod-shaped movable interrupting contact separable from said intermediate contact along said arcing passage to establish an interrupting arc progressively along said arcingpassage, a plurality of inlet passages leading into said arcing passage, means interconnecting the inlet passages with the pressure-generating arc, a normally open first venting means communicating with the arcingpassage and leading to the region exteriorly of the unit, said normally open first venting means being open during lengthening of the interrupting arc, a plurality of spaced exhaust passages leading away from the arcing passage, 21 second venting means connecting the exhaust passages with the region exteriorly of the unit, and valve means responsive to the pressure within the unit for opening said second venting means.

6. A circuit interrupter including an arc-extinguishing unit immersed in an arc-extinguishing liquid, at pressuregenerating contact separable from an intermediate contact to establish a pressure-generating arc, an arcing passage, a rod-shaped movable interrupting contact separable from said intermediate contact along said arcing passage to establish an interrupting arc progressively along said arcing passage, a plurality of inlet passages leading into arcing passage, means interconnecting the inlet passages with the pressure-generating arc, a normally open first venting means communicating with the arcing passage and leading to the region exteriorly of the unit, said normally open first venting means being open during lengthening of the interrupting are, a plurality of spaced exhaust passages leading away from the arcing passage, 21 second venting means connecting the exhaust passages with the region exteriorly of the unit, valve means responsive to the pressure within the unit for opening said second venting means, and each exhaust passage having a restriction therein immediately adjacent the arcing passage so that the rod-shaped movable interrupting contact will automatically function as a slide valve in successively uncovering the exhaust passages during the opening operation.

7. A circuit interrupter including an arc-extinguishing unit immersed in an arc-extinguishing liquid, at pressuregenerating contact separable from an intermediate contact to establish a pressure-generating are, an arcing passage, a rod-shaped movable interrupting contact separable from said intermediate contact along said arcing passage to establish an interrupting arc progressively along said arcing passage, a plurality of inlet passages leading into said arcing passage, means interconnecting the inlet passages with the pressure-generating arc, a normally open first venting means communicating with the arcing passage at all times and leading to the region exteriorly of the unit, a plurality of spaced exhaust passages leading away from the arcing passage, and a slide valve responsive to the pressure Within the unit for controlling the exhausting of liquid out through the exhaust passages.

8. A circuit interrupter including an arc-extinguishing unit immersed in an arc-extinguishing liquid, a pressuregenerating contact separable from an intermediate contact to establish a pressure-generating are, an arcing passage, a rod-shaped movable interrupting contact separable from said intermediate contact along said arcing passage to establish an interrupting arc progressively along said arcing passage, a plurality of inlet passages leading into said arcing passage, means interconnecting the inlet passages With the pressure-generating arc, a normally open first venting means communicating with the arcing passage at all times and exhausting liquid out of the unit, a plurality of spaced exhaust passages leading away from the arcing passage, a slide valve responsive to the pressure within the unit for controlling the exhausting of liquid out through the exhaust passages, and each exhaust passage having a restriction therein immediately adjacent the arcing passage so that the rod-shaped movable interrupting contact will automatically function as a slide valve in successively uncovering the exhaust passages during the opening operation.

9. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating arc and an interrupting are within the unit, a first venting means associated with the interrupting arc and open during lengthening of the interrupting arc to the region exteriorly of the unit, a normally closed second venting means associated with the interrupting are independent from the first venting means for exhausting fluid to the exterior of the unit at a different location from the exhaust of fluid from said first venting means, valve means actuated at a predetermined pressure within the arc-extinguishing unit to open the normally closed second venting means, and passage means arranged so that fluid exhausting out of the unit through the second venting means will engage the interrupting are to assist in its extinction.

10. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating arc and an interrupting are within the unit, a first normally open venting means associated with the interrupting arc and open at all times to the region exteriorly of the unit, a normally closed second venting means associated with the interrupting are independent from the first venting means for exhausting fluid exteriorly of the unit at a different location from the exhaust of fluid from the first venting means, valve means actuated at a predetermined pressure within the arc-extinguishing unit to open the normally closed second venting means, and passage means arranged so that fluid exhausting out of the unit through the second venting means will engage the interrupting arc to assist in its extinction.

11. A circuit interrupter of the fluid-blast type including an arc-extinguishing unit, means for establishing a pressure-generating are and an interrupting are within the unit, an interrupting structure disposed adjacent the interrupting arc and having spaced exhaust passages with a first venting means associated therewith to exhaust fluid out of the unit, a normally closed second venting means associated with the interrupting are independent from the first venting means including spaced other exhaust passages to exhaust fluid at a different location from the exhaust of fluid from the first venting means, valve means actuated at a predetermined pressure Within the arcextinguishing unit to open the normally closed second venting means, and the interrupting structure causing the fluid exhausting out of the second venting means to engage and help extinguish the interrupting arc.

References Cited in the file of this patent UNITED STATES PATENTS 2,465,218 Friedrich Mar. 22, 1949 2,501,318 Cumming Mar. 21, 1950 2,519,772 Latour Aug. 22, 1950 2,606,262 Bartlett Aug. 5, 1952 

